In recent years, automobile racing has become one of the most popular sporting events in the United States and abroad. Auto racing's popularity is evidenced by the number of weekend auto races, extensive fan support and corporate sponsorship, and 24-hour cable television coverage. In addition, the sport's popularity is seen in the wide variety of race series available for drivers and spectators, including the Indy Racing League (IRL), NASCAR's car and truck series, FORMULA 1, CART, and IROC.
In automobile racing, high-performance vehicles travel many times around an oval track at very high speeds. Many of these tracks utilize outer retaining or containment walls, typically in the form of substantially rigid concrete barriers, to prevent race vehicles from leaving the track. Unfortunately, race vehicles frequently lose control and impact the rigid outer containment wall, resulting in high-impact energies and, occasionally, driver injuries and fatalities. Errant vehicles and driver injuries and fatalities do not occur only on race tracks, but on highways, interstates, autobahns, and other public roadways in the United States and abroad. An improved barrier system can mitigate the severity of high-speed, high-energy automobile accidents and potentially reduce the number of injuries and fatalities on race tracks and public roadways.
Over the years, there have been many efforts to advance the state of the art of safety barrier design and construction. Some of the simpler proposed solutions consisted of loosely-stacked foam blocks placed around the outer, exterior walls of the track or roadway to reduce the severity of impact between the errant vehicle and the rigid wall. An impacting vehicle, however, can penetrate these foam blocks and strike the retaining wall with little or no impact energy having been absorbed by the blocks. Further, portions of the foam blocks can be knocked onto the track or roadway by the impacting vehicle, creating a hazard for other vehicles that follow. Other barrier designs have incorporated used rubber automobile tires banded together at selected regions of road courses. Although these tire barriers offer significant impact attenuation, these systems capture virtually all impacting vehicles, significantly increasing the total velocity change during the crash and greatly increasing the risk of driver injury or fatality. Further, tire barriers can allow vehicles to under-ride the barrier and lead to intrusion into the vehicle's occupant compartment. This type of system is generally appropriate only for locations where vehicle redirection is not practical, such as the gore areas created at tight hairpin turns.
In the late 1990's, a barrier system known as the FLAG barrier was developed. The FLAG barrier was a compression-type barrier consisting of large diameter, thick-walled resilient cylinders attached to a rigid concrete racetrack wall. The cylinders were placed adjacent one another, forming a longitudinal row of cylinders positioned along the track side. Smaller diameter cylinders were placed on the traffic-side face of the longitudinal barrier and positioned and attached at the recessed regions between the larger cylinders to minimize the potential for vehicle pocketing. This barrier system was crash tested using a 1,248 kg vehicle impacting at a speed of 121.0 km/hr and an angle of 20.8 degrees. After compressing several of the cylinders, the test vehicle was smoothly redirected, exiting the system at a speed of 70.0 km/hr and an angle of 15.0 degrees. However, the vehicle's velocity change and exit angle were both relatively high.
In 1998, a polyethylene energy dissipating system (PEDS) was developed for use on oval racetracks. The PEDS barrier system was configured using high-density polyethylene (HDPE) cylinders covered by a thick HDPE skin on the front and top of the cylinders. To expedite construction and repair of the PEDS system, the barrier was designed and fabricated in modular units attached to the concrete wall using a cable restraint system. The cover skin was used to reduce the potential for vehicle pocketing in the front face and reduce or eliminate the potential for the driver's extremities becoming caught in the openings between the cylinders. During the running of an IROC race at the Indianapolis Motor Speedway in August, 1998, driver Arie Luyendyk was involved in a crash which resulted in his IROC car impacting rearward on the PEDS barrier installed downstream from the inside corner of turn four. The estimated impact condition for this event consisted of a 1,633 kg car striking the barrier at a speed of 209 km/hr and an angle of 32 degrees. Remarkably, the driver sustained no serious injury from this severe impact event. These relatively positive results were attributed to the PEDS barrier and the excellent energy management of IROC vehicles during rearward impacts. The PEDS barrier, however, sustained significant damage, and debris was spread across the racing surface. Based on the impact performance of the PEDS barrier, several modifications were made to increase its energy-absorbing capabilities and prevent the units from becoming dislodged.
Beginning in 1999, researchers at the Midwest Roadside Safety Facility (MwRSF) in Lincoln, Nebr. in cooperation with IRL and NASCAR, investigated several energy-absorbing barrier concepts for use in high-speed racetrack and roadway applications using both computer simulation modeling and full-scale vehicle crash testing. The energy-absorbing properties and potential of both HDPE and foam materials were investigated. This testing and simulation indicated that HDPE barrier systems allowed impacting vehicles to gouge into the material and create snagging and pocketing, indicating to the MwRSF researchers that HDPE barrier faces offered no improvements or advantages over concrete barriers.
Simulation and testing of vehicle barriers indicates that lateral accelerations imparted to impacting vehicles and their occupants can be greatly reduced by adding even modest amounts of energy dissipation to rigid barrier systems. Further, testing has indicated that the utilization of relatively stiff longitudinal barrier elements would minimize vehicle rebound from the barrier. Subsequently, an energy-absorbing barrier system utilizing rubber energy absorbers with steel reinforced fiberglass fender panels was developed. This barrier design included a cable and strut mechanism by which the fender panels were attached to the vertical concrete backup structure to allow the barrier to deflect rearward with limited longitudinal motion. However, the relatively short “fish scale” fender panels and the soft energy absorbers utilized in this barrier caused the system to deform around the front of the impacting vehicle, increasing the potential for snagging and/or high rebound angles at increased impact speeds. Further, the cables and struts used to mount the barrier to the backup structure also posed potential snagging problems during high-speed impacts.